API RP 11V8:2003 pdf download

API RP 11V8:2003 pdf download.Recommended Practice for Gas Lift System Design and Performance Prediction.
Gas lift valve installation and reir,eval methods are:
• Conventional valves and mandrels installedreiriesed with the tubing.
• Wireline instalkdrethesed valves set inside the pocket of a side-pocket mandrel in the tubing string.
• Special valves and mandrcls instalkdrcuicvcd with coiled tubing.
Imporiwit. fundamental concepts abuut salves. Figure 1-3.
• Valves control thc point of entry of thc iwc-.scd gas into the production siring and act as a pressure regulator.
• Valves have cross-sectional ares at the bellows (4) and at the stempon (A,,) that pressure acts on:
— nitrogen pressure (Ps,) andot- a speng lotte,. the stcmball to close on the pon scat.
– injection gas (Ps) and fluid production IP1) pressures provide the cowitcr forces that act to upen the salve.
• Valve pon size may be a constraint to the masimum amount of injected gas, but the upimum gas rate is adjusted with the surface injection choke or controller (a choke in the valve can also be used).
• A reset-se flow check salve, mounted below the pod of the valve. prevents flow from the production fluid conduit hack into the gas column Inot shown I,
An orifice can be used in lieu of a valve at the espected depth of injection. The orifice consists of the orifice iporu and the reserve flow check, but does not have a bellows and stein, so it is not a salve that can open or close.
Usually, the gas lift salve allows the injection gas to flow from the tubing-casing annular space into the production tubing. Hut alternatively, a gas lift valve can be installed to allow the gas to flow liven the tubing into the annular space where it mises with the production fluids coming from the reservoir. This is done when the gas and oil flow rates are high and require the annular area to minimize pressure loss. Casing corrosion due to annular flow is difficult to remedy. thus flow up the casing annulus is u%ually not recomnwnded and often prohibiteL
C. as and liquid ;athcring System
The multiphase gas-liquid flow (miii the well is transported either direcdy ui through a gathering manifold to a separator station. Pipeline (fkiwlinc) sizing is dependent on the connection method:
• Directly connected flowlines—thc diameter of the gas oiLwater pipeline dcpentis on the flow rate, topography.
– must be cotyoct between valve inandrels or the unloading stops prematurely and eIfecus’e. deep lift is not attained.
• Gas lift valve pressure sdfling.s:
– are based on a specified gas injection plessure.
• are affected b salve type and site.
pennit the salve to close .ttter unloading and trinsrening to the next deeper salve.
• Valve pnn sue and gasfluid pressures influence the gas flow throughput. but primary control is by the surface chu&e cw controller.
• An injection pressure operated salve (IPO) will react mainly to the gas injection pressure.
• A production pressure operated valve fPPOI will react primarily to the production fluid pressure,
The system can he operated with continuous injection into each well or with intennitrent injection into some wells, pro- sided the puking gas pressure does not adversely affect the continuous flow wells.
2 Types of Gas Lift Systems
The gas lift system type will bc determined by thc most effective gas lift method. conunuous or intermittent. Cbnicc is based on the well and the gas distribution system conditions:
• Producing rate and tubing diameter.
• Static hottomholc pressure ISBHP.
• Gas piping diameter.
• (las injection pressure and available rule.
Intenninent lift applies only when rate. SBIIP. andur Pt arc too kw for etIcctise continuous gas lift. The choice is related to the tubing sIZC as well. since continuous flow might be maintained by reducing tubing diameter to increase fluid velocity.
Water or gas coning or sand production may influence selcction:
• Steady continuous how is preferrcti
• Pulsating ilitermittent flow aggravates an existing sand production problem.
• (ia.s piping restrictions are greater constr.tint’s with iflteflflittellt lift.
• Surging continuous flow contributes to these same problems.